Low-methoxyl polyvalent metal pectinate fibers



Patented Jan. 31, 1950 UNITED STATES PATENT OFFICE 'LOW- METHOXYLPOLYVALENT PECTINATE FIBERS Harry S. Owens, Berkeley, and Harry Lotzkar,Los Angeles, Calif., assignors to 'UnitedStates of America asrepresented by the Secretary of Agriculture N Drawing. ApplicationNov'ernber22, 1946, Serial No. 711,763

(Granted under the act of March 3, *1883,-as amended April 30, 1928;3'70 0. G. 757) 3 Claims.

'1 This application is made under the act of March 3, 1883, as amendedby the act of April 30, 1928', and the invention herein described andclaimed, if patented, may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment to us-of any royalty thereon. This invention relatesto the preparation of 'fibers from pectinic acids.

An object of this invention is to provide a process for preparing fiberscomposed of polyvalent metal salts of pectinic acids.

Another object of this invention is to provide fibers composed ofpolyvalent metal salts of this invention are derived from pectinic acidswhich in turn are derived from pectin. Pectin is produced in'largequantities from citrus peel and apple pomace. From the pectin by a demethoxylation procedure, low-methoxyl pectinic acids are made. Forinstance in U. S. Patent No. 2,358,430 to Willaman et al., September 19,1944, is shown a'method for de-methoxylating pectin by an enzymichydrolysis. These lowmethoxyl pectinic acids may also be prepared frompectin by alkaline or by acid hydrolysis.

Since'there isconsiderable confusion with respect to naming thesubstances involved herein, it may be of interest to define some of theterms used. By pectin is meant the usual preparation of commerceextracted from various plant sources such as citrus peel or apple pomacewithout substantial de-methoxylation. By pectic acid is meant asubstantially completely demethoxylated pectin. By pectinic acid ismeant a derivative of pectin with a methoxyl content intermediatebetween that of pectin and that of pectic acid.

The fibers of the instant invention are in the form of the saltsof'pectinic acids with polyvalent metals. In order to prepare thesefibers an aqueous solution of pectinic acids, or a partially neutralizedsolution of pectinic acids, is

The pectinic acid used in this example contained 3.5% methoxyl and wasprepared by enzymic de-methoxylation'of. pectin. A 1% solu- 'tion of thepectinic acid was prepared by stirring the :pectinic :acid with therequisite amount of water and sufficientsodium hydroxide to give a final.pH of 5.0. This partially-neutralized solution of pectinic acid wascentrifuged to remove air bubbles-and suspended matter,.andthen extrudedthrough a nozzlehaving'an opening 1 mm. in diameter into .a bath of 1normal'solution of zinc chloride in'95.% ethanol. The fiber so producedwas soaked'overnight in ethanol and then stretched 47% by suspendingthe-fiber and attaching'a weight to-the end thereof. The fiber was thendried and placed in an atmos- 'phere of relative humidity 65% at 25 C.for 24 hours. The fiber which had a diameter of 0.015

'mm. was found to have a tensile strength oi 44,000 lbs/sq. in. The wetstrength was found to be 9100 lbs/sq. in.

Example 2.Calcium pectinate fiber Calcium pectinate fibers were preparedin manner similar to that set forth in Example 1. Thus a calciumpectinate fiber derived from pectinic'acids (3.5% methoxyl contentprepared by enzymic demethoxylation of pectin), spun in a 1 normalcalcium chloride-% ethanol bath,

and stretched-44% had a diameter of- 0.0l5 mm.

and was found to have a tensile strength of 49,000 lbs/sq. in. Thisfiber when wet had a tensile strength of 9,000 lbs/sq. in.

Example 3.C'dlcium pectinate fiber The pectinic acid used in'this-example'hada methoxyl content of 3.0% and was prepared by alkalinede-methoxylation of pectin. A 1% solution of thepectinic acid wasprepared-by stirring with the requisite amount of waterand sufiicientsodium hydroxide to give a final pH of 4 to 5. Thesolution of partiallyneutralized pectinic acid was centrifuged to remove air bubbles andsuspended matter and extruded through .a nozzle having an opening 1mm.'in diameter. The precipitation bath was a 1 normal calcium chloridesolution in water. The fiber was washedwith very dilute (0.025 N)hydrochloric acid. This procedure yielded a:good,-continuous-fibercomposed of calcium salts-of low-methoxyl pectinic acids.

Example "4.Calcium Jpectin'ate fiber The process of Example 3 wasrepeated using as the precipitating bath a 1 normal solution of calciumchloride in water, adjusted to 0.2 normal with respect to hydrochloricacid. A continuous, strong fiber of calcium pectinate obtained.

Example 5.C'alcium pectinate fiber A calcium pectinate fiber wasprepared as described in Example 1 from a pectinic acid having amethoxyl content of 7.9% and prepared by enzymic de-methoxylation ofpectin. The fiber was stretched 46% and had a diameter of 0.01 mm. and atensile strength of 44,000 lbs./sq. in.

Example 6.-Zz'nc pectinate fiber A zinc pectinate fiber was prepared asdescribed in Example 1, from a pectinic acid having a methoxyl contentof 7.9% and prepared by enzymic demethoxylation of pectin. The fiber wasstretched 56%, had a diameter of 0.011 and a tensile strength of 34,000lbs/sq. in.

It has been shown above how to prepare the calcium and zinc pectinatefibers. In similar manner, other metal pectinate fibers can be produced.By merely changing the salt in the precipitating bath, other polyvalentmetal pectinate fibers can be prepared. Thus in order to prepare copper,ferric, or chromium pectinate fibers, the bath should contain copperchloride, ferric chloride, or chromic chloride, respectively. Ifdesired, mixtures of various polyvalent metal salts can be used in thebath to obtain a fiber of mixed polyvalent metal composition.

The fiber need not necessarily be stretched. However, it has beenobserved that in general stretching the fiber from 20 to 80% impartsconsiderable increase in the tensile strength of the fiber.

The dry tensile strength of the fibers herein disclosed has been foundto vary from 20,000 to 70,000 lbs/sq. in. with an average strength of40,000 lbs./ sq. in. This obviously compares very favorably with thenatural and synthetic fibers, for instance, wool which has a tensilestrength of 21,000 to 38,000 lbs/sq. in. The wet strength of thepolyvalent metal pectinate fibers is somewhat low being about 20% of thedry strength.

The concentration of pectinic acids in the spinning solution may bevaried within fairly wide limits. Concentrations of from 1% to 8% havebeen found to give the best results. Pectim'c acids of high molecularweight such as those prepared by enzymic de-methoxylation of pectinproduce solutions which are too viscous to be handled readily and inusing such pectinic acids, concentrations of about are the maximum.

In order to bring the pectinic acid into solution and in order to get asolution liquid enough so that it can be spun, a small amount of sodiumhydroxide or other alk-ali must often be added. Whether the alkali isnecessary or not depends on the methoxyl content of the pectinic acidand the method by which it was prepared. If the pectinic acid wasprepared by alkaline or acid de-methoxylation of pectin, no alkali isnecessary if the methoxyl content is above about 5.0%. If, however, themethoxyl content is lower than about 5.0%, alkali must be added to bringthe pectinic acids into solution Enough alkali is added to bring thefinal pH to about 3.8 to 6.0. The pectinic acids prepared by enzymicde-methoxylation are much more insoluble than those mentioned above. Inusing pectinic acids made by the enzymic process, alkali must be addedif the methoxyl content of the pectinic acid is lower 4 than about 8%.Again, sufficient alkali should be added to bring the pH to about 3.8 to6. With those pectinic acids which are soluble enough in water toproduce a solution, liquid enough to be spun, no addition of alkali isnecessary.

The precipitating bath should be an aqueous solution of a polyvalentmetal salt. It is preferred to have a considerable proportion of alcohol(-or other water-soluble organic solvent such as isopropyl alcohol oracetone) present in this bath and thereby it will satisfactorilyprecipitate pectinic acids of any methoxyl content. Where the alcohol,or other solvent, is omitted, the bath will satisfactorily precipitatepectinic acids having a methoxyl content up to about 6%. Theconcentration of salt in the bath is not critical.

The process is applicable to pectinic acids having a wide range ofmethoxyl content from 3% to about 10%.

The fibers of this invention may be employed in any of the usualapplications of natural and synthetic fibers, such as weaving orknitting textiles. The calcium pectinate fiber can be employed as asuture as it is non-allergenic.

The fibers can be dyed readily, more so than many natural and syntheticfibers. The polyvalent metal pectinate fibers can be dyed readily withacid dyes as there is a reaction between the metal cations and the aciddyestuff.

Cloth woven from the polyvalent metal pectinate fibers is much morefire-resistant than is cotton or rayon textiles.

Having thus described our invention, we claim:

1. An artificial fiber having a wet tensile strength of not less thanabout 9,000 pounds per square inch cross section comprising essentiallya filament of calcium salt of a pectinic acid having a methoxyl contentof 3 to 7.9

2. An artificial fiber having a dry tensile strength not less than about20,000 pounds per square inch cross section comprising essentially afilament of a polyvalent metal salt of a pectinic acid having a methoxylcontent of 3 to 7.9%.

3. An artificial fiber having a dry tensile strength not less than about20,000 pounds per square inch cross section comprising essentially afilament of zinc salt of a pectinic acid having a, methoxyl content of 3to 7.9

HARRY S. OWENS. HARRY LOTZKAR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,132,065 Wilson Oct. 4, 19382,132,577 Olsen et a1 Oct. 11, 1938 2,155,361 Myers Apr. 18, 19392,371,717 Speakman Mar. 20, 1945 2,418,866 Bryant Apr. 15, 19472,448,818 McCready et al Sept. 7, 1948 OTHER REFERENCES Palmer et al.,J. A. C. 8., vol. 67 (1945), page 883; 1 page.

2. AN ARTIFICIAL FIBER HAVING A DRY TENSILE STRENGTH NOT LESS THAN ABOUT20,000 POUNDS PER SQUARE INCH CROSS SECTION COMPRISING ESSENTIALLY AFILAMENT OF A POLYVALENT METAL SALT OF A PECTINIC ACID HAVING A METHOXYLCONTENT OF 3 TO 7.9%.